Method for improving cement toughness

ABSTRACT

This document relates to methods for providing long-term zonal isolation in oil wells using cement compositions that contain triazine-based polymeric additives. The cement compositions containing the polymeric additives exhibit increased tensile strength, elastic strength, or both, without suffering a decrease in compressive strength, as compared to the same cement without the polymeric additive.

TECHNICAL FIELD

This disclosure describes improvements to wellbore cements and methodsfor using such improved wellbore cements.

BACKGROUND

Well cementing is an important operation during drilling and completionof oil wells. The cement sheath must maintain well integrity behind thecasing and provide long-term zonal isolation to ensure safety andprevent environmental problems. The cement placed in the annulus betweenthe casing and the formation experiences frequent stresses, such asvarying or extreme temperatures and pressures. These frequent stressescan deteriorate the mechanical properties of the cement over a period oftime and lead to formation of micro-cracks and fractures, thus affectingthe production and increasing the cost of operation.

Since cement tends to fracture under downhole conditions due to thebrittleness of the cement in its neat form, polymeric additives,including polymeric and organic-inorganic hybrid material-basedadditives, have been added to the cement in an attempt to improve theelastic properties. Generally, the polymeric additives bind cementparticles through weak physical bonding, for example, electrostatic orhydrogen bonding. While these additives have substantially improved thetensile properties of the cement, such additives tend to impart asignificantly negative attribute to the cement in the form of areduction in compressive strength.

Therefore, there is a need for additives and methods that improve thetensile properties of cement, while having a minimum impact on thecompressive strength, for adequate long-term zonal isolation in oilwells.

SUMMARY

Provided in this disclosure are polymeric additives, cementcompositions, and methods for treating subterranean formations. Thecement compositions containing the polymeric additives exhibit increasedtensile strength, elastic strength, or both, without suffering adecrease in compressive strength, as compared to the same cement withoutthe polymeric additive. Also provided are methods of using such cementcompositions in the long-term zonal isolation of oil wells.

Provided in this disclosure is a method for preventing the formation ofmicro-cracks and fractures in the cement of an oil well, therebyproviding long-term zonal isolation in the well, the method includingproviding to an oil well a cement composition that contains cement and atriazine polymeric additive selected from a polymer with repeat unit Aand a polymer with repeat unit B:

where R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and n is about 10 to about 1000, about50 to about 500, or about 100 to about 200; where the cement compositionexhibits improved elastic properties as compared to the same compositionwithout the polymeric additive.

In some embodiments of the method, R¹ is selected from the groupconsisting of:

where R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to 8. In some embodiments, R¹ is

In some embodiments of the method, the polymeric additive is a polymerwith repeat unit A and has the structure:

In some embodiments of the method, the polymeric additive is a polymerwith repeat unit B and has the structure:

In some embodiments of the method, the amount of polymeric additive inthe cement composition is between about 0.1% to about 10% by weight ofthe cement. In some embodiments, the amount of polymeric additive in thecement composition is about 3% by weight of the cement.

In some embodiments of the method, the cement composition also containsone or more of a suspending agent, a neutralizing agent, and a reactionpropagating agent. In some embodiments, the one or more suspendingagent, neutralizing agent, and reaction propagating agent are selectedfrom the group consisting of N,N-diisopropylethylamine, triethylamine,trimethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate,and potassium carbonate.

In some embodiments of the method, the cement composition also containswater.

In some embodiments of the method, the cement composition has a Young'smodulus of about 0.1 gigapascals (GPa) to about 40 GPa, about 3 GPa toabout 25 GPa, or about 5 GPa to about 20 GPa at a pressure of about 0.1megapascal (MPa) to about 150 MPa, about 10 MPa to about 100 MPa, orabout 20 MPa to about 40 MPa, at a temperature of about 77° F. to about450° F., about 125° F. to about 350° F., or about 150° F. to about 200°F. In some embodiments, the cement composition has a Young's modulus ofabout 5 GPa to about 10 GPa at a pressure of about 20 MPa and atemperature of about 180° F.

In some embodiments of the method, the cement composition has acompressive strength of about 1000 pounds per square inch (psi) to about10,000 psi, about 2000 psi to about 8000 psi, or about 3500 psi to about6500 psi, at a pressure of about 0.1 MPa to about 150 MPa, about 10 MPato about 100 MPa, or about 20 MPa to about 40 MPa, at a temperature ofabout 77° F. to about 450° F., about 125° F. to about 350° F., or about150° F. to about 200° F. In some embodiments, the cement composition hasa compressive strength of about 5500 psi to about 6500 psi at a pressureof about 20 MPa and a temperature of about 180° F. In some embodiments,addition of the polymeric additive to the cement does not decrease thecompressive strength of the cement by more than about 200 psi to about1000 psi as compared to the compressive strength of the same cementwithout addition of the polymeric additive.

Also provided is a cement composition for providing long-term zonalisolation in oil wells, comprising cement; and a triazine polymericadditive selected from a polymer with repeat unit A and a polymer withrepeat unit B:

where R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and n is about 10 to about 1000, about50 to about 500, or about 100 to about 200.

In some embodiments, le is selected from the group consisting of:

where R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to 8. In some embodiments, R¹ is

In some embodiments, the polymeric additive is a polymer with repeatunit A and has the structure:

In some embodiments, the polymeric additive is a polymer with repeatunit B and has the structure:

In some embodiments, the amount of polymeric additive in the cementcomposition is between about 0.1% to about 10% by weight of the cement.In some embodiments, the amount of polymeric additive in the cementcomposition is about 3% by weight of the cement.

In some embodiments, the cement composition also contains one or more ofa suspending agent, a neutralizing agent, and a reaction propagatingagent. In some embodiments, the one or more suspending agent,neutralizing agent, and reaction propagating agent are selected from thegroup consisting of N,N-diisopropylethylamine, triethylamine,trimethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate,and potassium carbonate.

In some embodiments, the cement composition also contains water.

In some embodiments, the cement composition has a Young's modulus ofabout 0.1 GPa to about 40 GPa, about 3 GPa to about 25 GPa, or about 5GPa to about 20 GPa at a pressure of about 0.1 MPa to about 150 MPa,about 10 MPa to about 100 MPa, or about 20 MPa to about 40 MPa, at atemperature of about 77° F. to about 450° F., about 125° F. to about350° F., or about 150° F. to about 200° F. In some embodiments, thecement composition has a Young's modulus of about 5 GPa to about 10 GPaat a pressure of about 20 MPa and a temperature of about 180° F.

In some embodiments, the cement composition has a compressive strengthof about 1000 psi to about 10,000 psi, about 2000 psi to about 8000 psi,or about 3500 psi to about 6500 psi, at a pressure of about 0.1 MPa toabout 150 MPa, about 10 MPa to about 100 MPa, or about 20 MPa to about40 MPa, at a temperature of about 77° F. to about 450° F., about 125° F.to about 350° F., or about 150° F. to about 200° F. In some embodiments,the cement composition has a compressive strength of about 5500 psi toabout 6500 psi at a pressure of about 20 MPa and a temperature of about180° F.

Also provided in the present disclosure is a method of preparing acement composition, comprising: a) reacting a difunctional monomer withcyanuric chloride to form a triazine polymeric additive; and b) mixingthe triazine polymeric additive with cement.

In some embodiments of the method, the difunctional monomer is selectedfrom the group consisting of a cyclic aliphatic secondary amine, anaromatic diamine, an aromatic diol, an aliphatic diamine, and analiphatic diol. In some embodiments, the difunctional monomer isselected from the group consisting of:

where R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to 8. In some embodiments, the difunctional monomer is

In some embodiments of the method, the molar ratio of the cyanuricchloride to the difunctional monomer is about 1:1 to about 1:2. In someembodiments, the molar ratio of the cyanuric chloride to thedifunctional monomer is about 1:1. In some embodiments, the triazinepolymeric additive has the structure:

where n is about 10 to about 1000, about 50 to about 500, or about 100to about 200. In some embodiments, the molar ratio of the cyanuricchloride to the difunctional monomer is about 1:1.5. In someembodiments, the triazine polymeric additive has the structure:

where n is about 10 to about 1000, about 50 to about 500, or about 100to about 200.

In some embodiments of the method, the amount of polymeric additive inthe cement composition is about 0.1% to about 10% by weight of thecement. In some embodiments, the amount of polymeric additive in thecement composition is about 3% by weight of the cement.

In some embodiments of the method, the cement composition also containsone or more of a suspending agent, a neutralizing agent, and a reactionpropagating agent. In some embodiments, the one or more suspendingagent, neutralizing agent, and reaction propagating agent are selectedfrom the group consisting of N,N-diisopropylethylamine, triethylamine,trimethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate,and potassium carbonate.

In some embodiments of the method, the cement composition also containswater.

DESCRIPTION OF DRAWINGS

FIGS. 1A-1B illustrate two examples of polymeric additives. FIG. 1Ashows a linear, ladder-type polymeric structure. FIG. 1B shows anexample of a non-linear, branched polymeric structure.

FIG. 2 shows the FT-IR spectra for POLY A and POLY B.

FIGS. 3A-3B depicts the thermogravimetric analyses of POLY A (FIG. 3A)and POLY B (FIG. 3B).

FIG. 4 shows the compressive strengths of cement formulations A-C underconfined pressure of 20 MPa at 80° F. and 180° F.

FIG. 5 shows the FT-IR spectra of POLY A and Formulation C (POLY Ablended with cement).

FIG. 6 is a graph showing the Young's modulus of cement formulations A-Cunder confined pressure of 20 MPa at 80° F. and 180° F.

DETAILED DESCRIPTION

Reference will now be made in detail to certain embodiments of thedisclosed subject matter. While the disclosed subject matter will bedescribed in conjunction with the enumerated claims, it will beunderstood that the exemplified subject matter is not intended to limitthe claims to the disclosed subject matter.

The present application provides compositions, such as cementcompositions containing polymeric additives, and methods for improvingthe tensile properties, elastic properties, or both, of cement whilehaving minimum impact on the compressive strength (that is, toughness).Traditional polymeric additives typically do not have stronginteractions with the cement particles and instead form weak,interfacial interactions. Such interactions can be separated or rupturedunder stresses frequently encountered in downhole conditions, resultingin uneven distribution of stresses in the cement matrix and causingpropagation of cracks and failure of the mechanical properties of thecement sheath in the well.

The compositions and methods described in this document have enhancedtensile properties, elastic properties, or both, without a subsequentreduction of compressive strength due to the incorporation of polymericadditives, for example, triazine-based polymeric additives. In someembodiments, the polymeric additives are chemically reactive and formstrong, chemical linkages (that is, bonds) with the reactive pendentgroups on cement particles during curing of the cement. For example, thepolymeric additives can allow for molecular stretching within thepolymeric framework upon exerted stresses. In some embodiments, additionof the polymeric additives to cement restricts the propagation offractures in the cement under downhole conditions. In some embodiments,improvement in the elastic properties of the cement have been observedas compared to neat cement (that is, cement without the polymericadditives). In some embodiments, the compressive strength of the cementis not negatively affected upon addition of the polymeric additives.Thus, the compositions and methods described in this document aredesigned for use in long-term zonal isolation in oil wells, particularlyin severe conditions (for example, extreme temperatures, extremepressures, or both). In some embodiments, the cement compositions areable to maintain the uniform distribution of stress and provide wellborestability over long-term downhole conditions.

Definitions

Unless otherwise defined, all technical and scientific terms used inthis document have the same meaning as commonly understood by one ofordinary skill in the art to which the present application belongs.Methods and materials are described in this document for use in thepresent application; other, suitable methods and materials known in theart can also be used. The materials, methods, and examples areillustrative only and not intended to be limiting. All publications,patent applications, patents, sequences, database entries, and otherreferences mentioned in this document are incorporated by reference intheir entirety. In case of conflict, the present specification,including definitions, will control.

Values expressed in a range format should be interpreted in a flexiblemanner to include not only the numerical values explicitly recited asthe limits of the range, but also to include all the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range is explicitly recited. For example, arange of “about 0.1% to about 5%” or “about 0.1% to 5%” should beinterpreted to include not just about 0.1% to about 5%, but also theindividual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges(for example, 0.1% to 0.5%, 1.1% to 2.2%, and 3.3% to 4.4%) within theindicated range. The statement “about X to Y” has the same meaning as“about X to about Y,” unless indicated otherwise. Likewise, thestatement “about X, Y, or about Z” has the same meaning as “about X,about Y, or about Z,” unless indicated otherwise.

The term “about,” as used in this disclosure, can allow for a degree ofvariability in a value or range, for example, within 10%, within 5%, orwithin 1% of a stated value or of a stated limit of a range.

As used in this disclosure, the terms “a,” “an,” and “the” are used toinclude one or more than one unless the context clearly dictatesotherwise. The term “or” is used to refer to a nonexclusive “or” unlessotherwise indicated. The statement “at least one of A and B” has thesame meaning as “A, B, or A and B.” In addition, it is to be understoodthat the phraseology or terminology employed in this disclosure, and nototherwise defined, is for the purpose of description only and not oflimitation. Any use of section headings is intended to aid reading ofthe document and is not to be interpreted as limiting; information thatis relevant to a section heading may occur within or outside of thatparticular section.

In the methods described in this disclosure, the acts can be carried outin any order, except when a temporal or operational sequence isexplicitly recited. Furthermore, specified acts can be carried outconcurrently unless explicit claim language recites that they be carriedout separately. For example, a claimed act of doing X and a claimed actof doing Y can be conducted simultaneously within a single operation,and the resulting process will fall within the literal scope of theclaimed process.

As used in this disclosure, a “cement” is a binder, for example, asubstance that sets and forms a cohesive mass with measurable strengths.A cement can be characterized as non-hydraulic or hydraulic.Non-hydraulic cements (for example, Sorel cements) harden because of theformation of complex hydrates and carbonates, and may require more thanwater to achieve setting, such as carbon dioxide or mixtures of specificsalt combinations. Additionally, too much water cannot be present, andthe set material must be kept dry in order to retain integrity andstrength. A non-hydraulic cement produces hydrates that are notresistant to water. Hydraulic cements (for example, Portland cement)harden because of hydration, which uses only water in addition to thedry cement to achieve setting of the cement. Cement hydration products,chemical reactions that occur independently of the mixture's watercontent, can harden even underwater or when constantly exposed to wetweather. The chemical reaction that results when the dry cement powderis mixed with water produces hydrates that are water-soluble. Any cementcan be used in the compositions of the present application.

As used in this disclosure, the term “set” can mean the process of afluid slurry (for example, a cement slurry) becoming a hard solid.Depending on the composition and the conditions, it can take just a fewminutes up to 72 hours or longer for some cement compositions toinitially set.

As used in this disclosure, the term “C_(n-m) alkyl,” employed alone orin combination with other terms, refers to a monovalent saturatedhydrocarbon group that can be straight-chain (linear) or branched,having n to m carbons. Examples of alkyl moieties include, but are notlimited to, chemical groups such as methyl, ethyl, n-propyl, isopropyl,n-butyl, tert-butyl, isobutyl, sec-butyl; higher homologs such as2-methyl-1-butyl, n-pentyl, 3-pentyl, n-hexyl, and1,2,2-trimethylpropyl. In some embodiments, the alkyl group containsfrom 1 to 6 carbon atoms, from 1 to 4 carbon atoms, from 1 to 3 carbonatoms, or from 1 to 2 carbon atoms.

As used in this disclosure, the term “polymer” can refer to a moleculehaving at least one repeating unit and can include copolymers.

“Mechanical properties” of cement refer to the properties thatcontribute to the overall behavior of the cement when subjected to anapplied force, such as the frequent stresses cement is exposed to thatimpact its ability to both protect the casing and maintain zonalisolation. Mechanical properties of cement include compressive strength,elastic strength or the elastic modulus (that is, Young's Modulus),Poisson's ratio (the ratio of lateral strain to longitudinal strain in amaterial subjected to loading), and tensile strength.

The term “compressive strength” or “compression strength” refer to themeasure of the cement's ability to resist loads which tend to compressit or reduce size. Cement composition compressive strengths can varyfrom 0 psi to over 10,000 psi (0 to over 69 MPa). Compressive strengthis generally measured at a specified time after the composition has beenmixed and at a specified temperature and pressure. In some embodiments,compressive strength is measured by a non-destructive method thatcontinually measures correlated compressive strength of a cementcomposition sample throughout the test period by utilizing anon-destructive sonic device. For example, compressive strength of acement composition can be measured using the non-destructive methodaccording to ANSI/API Recommended Practice 10-B2 at a specified time,temperature, and pressure.

“Elastic strength,” as used in this disclosure, describes the ability ofthe cement to resist permanent deformation when force is applied.Elastic strength is also referred to as Young's Modulus. “Improvedelastic properties” means an increase in the elastic strength of thecement or cement composition being referred to.

The term “tensile strength,” as used in this disclosure, describes theability of the cement to resist breaking while being subjected totension forces. “Improved tensile properties” means an increase in thetensile strength of the cement or cement composition being referred to.

As used in this disclosure, “zonal isolation” means the prevention offluids, such as water or gas, in one zone of a well or subterraneanformation, from mixing with oil in another zone.

The term “downhole,” as used in this disclosure, can refer to under thesurface of the earth, such as a location within or fluidly connected toa wellbore.

As used in this disclosure, the term “subterranean formation” can referto any material under the surface of the earth, including under thesurface of the bottom of the ocean. For example, a subterraneanformation or material can be any section of a wellbore and any sectionof a subterranean petroleum- or water-producing formation or region influid contact with the wellbore. Placing a material in a subterraneanformation can include contacting the material with any section of awellbore or with any subterranean region that is in fluid contact withthe wellbore. Subterranean materials can include any materials placedinto the wellbore such as cement, drill shafts, liners, tubing, casing,or screens; placing a material in a subterranean formation can includecontacting with such subterranean materials. In some examples, asubterranean formation or material can be any below-ground region thatcan produce liquid or gaseous petroleum materials, water, or any sectionbelow-ground that is in fluid contact with liquid or gaseous petroleummaterials or water. In some embodiments, a subterranean formation is anoil well.

As used in this disclosure, “treatment of a subterranean formation” caninclude any activity directed to extraction of water or petroleummaterials from a subterranean petroleum- or water-producing formation orregion, for example, drilling, stimulation, hydraulic fracturing,clean-up, acidizing, completion, cementing, remedial treatment, andabandonment.

Cement Compositions Containing Polymeric Additives

Provided in this disclosure is a composition containing cement and apolymeric additive, for example, a triazine-based polymeric additive,that exhibits improved mechanical properties (for example, improvedelastic properties, tensile properties, toughness, compression strength,or a combination of such properties) as compared to the same cementcomposition that does not contain the polymeric additive. In someembodiments, the triazine-based polymeric additive improves thetoughness of the cement, for example, in the construction ofsubterranean oil and gas wells or for above-ground cement constructionapplications. In some embodiments, the composition contains one or moreadditional agents, such as a suspending agent, a neutralizing agent, ora reaction propagating agent. In some embodiments, the compositioncontains water.

Cement

The compositions of the present application contain cement and apolymeric additive, for example, a triazine-based polymeric additive.The cement can be any type of cement used in the construction ofsubterranean oil and gas wells, or any cement used in above-groundcement construction applications. In some embodiments, the cement isPortland cement. Examples of cements that can be used in thecompositions include, but are not limited to Class A, Class B, Class G,and Class H cements.

Polymeric Additive

In some embodiments, the polymeric additive is a triazine-basedpolymeric additive. The polymeric additive can be synthesized fromcyanuric chloride and a difunctional monomer. In some embodiments, thereaction between the cyanuric chloride and the difunctional monomerreleases hydrogen chloride to form the polymeric backbone.

The trifunctional monomer, cyanuric chloride, can be modified bysubstituting one or more of its three chloride groups at variousreaction temperatures. The temperature-dependent substitution of thechloride groups is shown in Scheme 1.

The first chloride group can be replaced by an X moiety at about 0° C.Subsequently, the second and third chloride groups can be replaced by Yand Z at about 15-30° C. and more than about 50° C., respectively. Insome embodiments, the temperature-dependent nucleophilic substitution ofcyanuric chloride is employed to synthesize a series of polymericadditives for use in the cement compositions described in the presentapplication. In some embodiments, one of the three chloride groups issubstituted with a difunctional monomer. In some embodiments, two of thethree chloride groups are substituted with a difunctional monomer. Insome embodiments, all of the three chloride groups are substituted witha difunctional monomer.

In some embodiments, the difunctional monomer that reacts with thecyanuric chloride to form the polymeric additive of the presentapplication is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol.

In some embodiments, the difunctional monomer is a cyclic aliphaticsecondary amine. Examples of cyclic aliphatic secondary amines include,but are not limited to piperazine, 4,4′-dipiperidine,4,4′-dimethylenedipiperidine, 4,4′-trimethylenedipiperidine,1,4-di(piperidin-4-yl)butane, 1,5-di(piperidin-4-yl)pentane,1,6-di(piperidin-4-yl)hexane, 1,7-di(piperidin-4-yl)heptane,1,8-di(piperidin-4-yl)octane, and homopiperazine. In some embodiments,the difunctional monomer is piperazine.

In some embodiments, the difunctional monomer is an aromatic diamine.Examples of aromatic diamines include, but are not limited tobenzene-1,2-diamine, benzene-1,3-diamine, benzene-1,4-diamine,benzidine, bis(4-aminophenyl)methanone, 4,4′-sulfonyldianiline,4,4′-oxydianiline, 4,4′-methylenedianiline,4,4′-(ethane-1,2-diyl)dianiline, 4,4′-(propane-1,3-diyl)dianiline,4,4′-(butane-1,4-diyl)dianiline, 4,4′-(pentane-1,5-diyl)dianiline,4,4′-(hexane-1,6-diyl)dianiline, 4,4′-(heptane-1,7-diyl)dianiline,4,4′-(octane-1,8-diyl)dianiline, naphthalene-1,5-diamine, andnaphthalene-2,6-diamine.

In some embodiments, the difunctional monomer is an aromatic diol.Examples of aromatic diols include, but are not limited to hydroquinone,resorcinol, pyrocatechol, [1,1′-biphenyl]-4,4′-diol,4,4′-methylenediphenol, 4,4′-(ethane-1,2-diyl)diphenol,4,4′-(propane-1,3-diyl)diphenol, 4,4′-(butane-1,4-diyl)diphenol,4,4′-(pentane-1,5-diyl)diphenol, 4,4′-(hexane-1,6-diyl)diphenol,4,4′-(heptane-1,7-diyl)diphenol, 4,4′-(octane-1,8-diyl)diphenol,naphthalene-1,5-diol, and naphthalene-2,6-diol.

In some embodiments, the difunctional monomer is an aliphatic diamine.Examples of aliphatic diamines include, but are not limited tomethanediamine, ethane-1,2-diamine, propane-1,3-diamine,butane-1,4-diamine, pentane-1,5-diamine, hexane-1,6-diamine,heptane-1,7-diamine, octane-1,8-diamine, and nonane-1,9-diamine.

In some embodiments, the difunctional monomer is an aliphatic diol.Examples of aliphatic diols include, but are not limited to methanediol,ethane-1,2-diol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol,hexane-1,6-diol, heptane-1,7-diol, octane-1,8-diol, and nonane-1,9-diol.

In some embodiments, the difunctional monomer is selected from the groupconsisting of:

where:

-   -   R² and R³ are each independently selected from the group        consisting of C₁-C₆ alkyl, C(═O), SO₂, and O;    -   m is 0 to 6;    -   p is 0 to 8; and    -   q is 0 to 8.

In some embodiments, the difunctional monomer is

In some embodiments, to obtain the desired polymer or polymericstructure, the synthesis of the polymeric additive is controlled, asdescribed in this disclosure and shown in Scheme 1, by controlling thereaction temperature. In other embodiments, the synthesis of thepolymeric additive is controlled by adjusting the molar ratio ofcyanuric chloride to difunctional monomer.

In some embodiments, the cyanuric chloride and difunctional monomerreact to form a polymeric additive that is a linear, ladder-type ofpolymer having a general structure as shown in FIG. 1A. This type ofpolymer can have reactive chloride groups on the polymeric chain (on thecyanuric chloride monomer). In some embodiments, the chloride groups ofthe polymeric additive react with cement particles, for example, thechloride groups react with the hydroxyl functional groups on the cementparticles, to form chemical bonds. In some embodiments, the otherfunctional groups (for example, nitrogen atoms) of the polymericadditive interact with the cement particles and form linkages. In someembodiments, the other functional groups (for example, nitrogen atoms)of the polymeric additive form electrostatic bonds with the cementparticles. In some embodiments, the polymeric additive has repeatingunits of the structure A:

where R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and

-   -   n is about 10 to about 1000, such as about 50 to about 500, or        about 100 to about 200.

In some embodiments, R¹ is one of the difunctional monomers described inthis disclosure. In some embodiments, R¹ is selected from the groupconsisting of:

where:

-   -   R² and R³ are each independently selected from the group        consisting of C₁-C₆ alkyl, C(=O), SO₂, and O;    -   m is 0 to 6;    -   p is 0 to 8; and    -   q is 0 to 8.

In some embodiments, n is an integer ranging in value from about 10 toabout 1000, such as about 10 to about 900, about 10 to about 800, about10 to about 700, about 10 to about 600, about 10 to about 500, about 10to about 400, about 10 to about 300, about 10 to about 200, about 10 toabout 100, about 10 to about 50, about 50 to about 1000, about 50 toabout 900, about 50 to about 800, about 50 to about 700, about 50 toabout 600, about 50 to about 500, about 50 to about 400, about 50 toabout 300, about 50 to about 200, about 50 to about 100, about 100 toabout 1000, about 100 to about 900, about 100 to about 800, about 100 toabout 700, about 100 to about 600, about 100 to about 500, about 100 toabout 400, about 100 to about 300, about 100 to about 200, about 200 toabout 1000, about 200 to about 900, about 200 to about 800, about 200 toabout 700, about 200 to about 600, about 200 to about 500, about 200 toabout 400, about 200 to about 300, about 300 to about 1000, about 300 toabout 900, about 300 to about 800, about 300 to about 700, about 300 toabout 600, about 300 to about 500, about 300 to about 400, about 400 toabout 1000, about 400 to about 900, about 400 to about 800, about 400 toabout 700, about 400 to about 600, about 400 to about 500, about 500 toabout 1000, about 500 to about 900, about 500 to about 800, about 500 toabout 700, about 500 to about 600, about 600 to about 1000, about 600 toabout 900, about 600 to about 800, about 600 to about 700, about 700 toabout 1000, about 700 to about 900, about 700 to about 800, about 800 toabout 1000, about 800 to about 900, about 900 to about 1000, or about10, about 25, about 50, about 75, about 100, about 150, about 200, about250, about 300, about 350, about 400, about 450, about 500, about 550,about 600, about 700, about 750, about 800, about 850, about 900, about950, or about 1000. In some embodiments, n is about 10 to about 1000. Insome embodiments, n is about 50 to about 500. In some embodiments, n isabout 100 to about 200.

In some embodiments, R¹ is

In some embodiments, the polymeric additive is a polymer with repeatingunits having the structure:

In some embodiments, cyanuric chloride reacts with piperazine, to form alinear, ladder-type polymer with the general structure:

where the wavy lines indicate further bonding to either a cyanuricchloride monomer or a piperazine monomer.

In some embodiments, the cyanuric chloride and difunctional monomerreact to form a polymeric additive that is a non-linear, branchedpolymer having a general structure as shown in FIG. 1B. This type ofpolymer lacks reactive chloride groups on the polymeric chain. In someembodiments, the polymeric additive forms physical bonds with the cementparticles. In some embodiments, the other functional groups (forexample, nitrogen atoms) of the polymeric additive interact with thecement particles and form linkages. In some embodiments, the otherfunctional groups (for example, nitrogen atoms) of the polymericadditive form electrostatic bonds with the cement particles. In someembodiments, the polymeric additive has repeating units of the structureB:

where R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and

-   -   n is about 10 to about 1000, such as about 50 to about 500, or        about 100 to about 200.

In some embodiments, R¹ is one of the difunctional monomers described inthis disclosure. In some embodiments, le is selected from the groupconsisting of:

where:

-   -   R² and Ware each independently selected from the group        consisting of C₁-C₆ alkyl, C(=O), SO₂, and O;    -   m is 0 to 6;    -   p is 0 to 8; and    -   q is 0 to 8.

In some embodiments, n is an integer ranging in value from about 10 toabout 1000, such as about 10 to about 900, about 10 to about 800, about10 to about 700, about 10 to about 600, about 10 to about 500, about 10to about 400, about 10 to about 300, about 10 to about 200, about 10 toabout 100, about 10 to about 50, about 50 to about 1000, about 50 toabout 900, about 50 to about 800, about 50 to about 700, about 50 toabout 600, about 50 to about 500, about 50 to about 400, about 50 toabout 300, about 50 to about 200, about 50 to about 100, about 100 toabout 1000, about 100 to about 900, about 100 to about 800, about 100 toabout 700, about 100 to about 600, about 100 to about 500, about 100 toabout 400, about 100 to about 300, about 100 to about 200, about 200 toabout 1000, about 200 to about 900, about 200 to about 800, about 200 toabout 700, about 200 to about 600, about 200 to about 500, about 200 toabout 400, about 200 to about 300, about 300 to about 1000, about 300 toabout 900, about 300 to about 800, about 300 to about 700, about 300 toabout 600, about 300 to about 500, about 300 to about 400, about 400 toabout 1000, about 400 to about 900, about 400 to about 800, about 400 toabout 700, about 400 to about 600, about 400 to about 500, about 500 toabout 1000, about 500 to about 900, about 500 to about 800, about 500 toabout 700, about 500 to about 600, about 600 to about 1000, about 600 toabout 900, about 600 to about 800, about 600 to about 700, about 700 toabout 1000, about 700 to about 900, about 700 to about 800, about 800 toabout 1000, about 800 to about 900, about 900 to about 1000, or about10, about 25, about 50, about 75, about 100, about 150, about 200, about250, about 300, about 350, about 400, about 450, about 500, about 550,about 600, about 700, about 750, about 800, about 850, about 900, about950, or about 1000. In some embodiments, n is about 10 to about 1000. Insome embodiments, n is about 50 to about 500. In some embodiments, n isabout 100 to about 200.

In some embodiments, R¹ is

In some embodiments, the polymeric additive is a polymer with repeatingunits having the structure:

In some embodiments, cyanuric chloride reacts with piperazine, to form anon-linear, branched polymer with the general structure:

where the wavy lines indicate further bonding to either a cyanuricchloride monomer or a piperazine monomer.

In some embodiments, the polymeric additive has a weight-averagemolecular weight of about 1 kilodalton (kDa) to about 2,500 kDa, forexample, a weight-average molecular weight of about 1 kDa to about 2,000kDa, about 1 kDa to about 1,500 kDa, about 1 kDa to about 1,000 kDa,about 1 kDa to about 750 kDa, about 1 kDa to about 500 kDa, about 1 kDato about 250 kDa, about 1 kDa to about 100 kDa, about 1 kDa to about 10kDa, about 10 kDa to about 2,500 kDa, about 10 kDa to about 2,000 kDa,about 10 kDa to about 1,500 kDa, about 10 kDa to about 1,000 kDa, about10 kDa to about 750 kDa, about 10 kDa to about 500 kDa, about 10 kDa toabout 250 kDa, about 10 kDa to about 100 kDa, about 100 kDa to about2,500 kDa, about 100 kDa to about 2,000 kDa, about 100 kDa to about1,500 kDa, about 100 kDa to about 1,000 kDa, about 100 kDa to about 750kDa, about 100 kDa to about 500 kDa, about 100 kDa to about 250 kDa,about 250 kDa to about 2,500 kDa, about 250 kDa to about 2,000 kDa,about 250 kDa to about 1,500 kDa, about 250 kDa to about 1,000 kDa,about 250 kDa to about 750 kDa, about 250 kDa to about 500 kDa, about500 kDa to about 2,500 kDa, about 500 kDa to about 2,000 kDa, about 500kDa to about 1,500 kDa, about 500 kDa to about 1,000 kDa, about 500 kDato about 750 kDa, about 750 kDa to about 2,500 kDa, about 750 kDa toabout 2,000 kDa, about 750 kDa to about 1,500 kDa, about 750 kDa toabout 1,000 kDa, about 1,000 kDa to about 2,500 kDa, about 1,000 kDa toabout 2,000 kDa, about 1,000 kDa to about 1,500 kDa, about 1,500 kDa toabout 2,500 kDa, about 1,500 kDa to about 2,000 kDa, about 2,000 kDa toabout 2,500 kDa, or about 1 kDa, about 10 kDa, about 50 kDa, about 100kDa, about 250 kDa, about 500 kDa, about 750 kDa, about 1,000 kDa, about1,250 kDa, about 1,500 kDa, about 1,750 kDa, about 2,000 kDa, about2,225 kDa, or about 2,500 kDa.

In some embodiments, the amount of polymeric additive in the cementcomposition is about 0.1% to about 10% by weight of the cement. Forexample, the polymeric additive can be about 0.1% to about 9%, about0.1% to about 8%, about 0.1% to about 7%, about 0.1% to about 6%, about0.1% to about 5%, about 0.1% to about 4%, about 0.1% to about 3%, about0.1% to about 2%, about 0.1% to about 1%, about 0.1% to about 0.5%,about 0.5% to about 10%, about 0.5% to about 9%, about 0.5% to about 8%,about 0.5% to about 7%, about 0.5% to about 6%, about 0.5% to about 5%,about 0.5% to about 4%, about 0.5% to about 3%, about 0.5% to about 2%,about 0.5% to about 1%, about 1% to about 10%, about 1% to about 9%,about 1% to about 8%, about 1% to about 7%, about 1% to about 6%, about1% to about 5%, about 1% to about 4%, about 1% to about 3%, about 1% toabout 2%, about 2% to about 10%, about 2% to about 9%, about 2% to about8%, about 2% to about 7%, about 2% to about 6%, about 2% to about 5%,about 2% to about 4%, about 2% to about 3%, about 3% to about 10%, about3% to about 9%, about 3% to about 8%, about 3% to about 7%, about 3% toabout 6%, about 3% to about 5%, about 3% to about 4%, about 4% to about10%, about 4% to about 9%, about 4% to about 8%, about 4% to about 7%,about 4% to about 6%, about 4% to about 5%, about 5% to about 10%, about5% to about 9%, about 5% to about 8%, about 5% to about 7%, about 5% toabout 6%, about 6% to about 10%, about 6% to about 9%, about 6% to about8%, about 6% to about 7%, about 7% to about 10%, about 7% to about 9%,about 7% to about 8%, about 8% to about 10%, about 8% to about 9%, about9% to about 10%, or about 0.1%, about 0.5%, about 1%, about 1.5%, about2%, about 2.5%, about 3%, about 3.5%, about 4%, about 4.5%, about 5%,about 5.5%, about 6%, about 6.5%, about 7%, about 7.5%, about 8%, about8.5%, about 9%, about 9.5%, or about 10% by weight of the cement. Insome embodiments, the polymeric additive is about 3% by weight of thecement.

Additional Components

In some embodiments, the cement composition also contains one or more ofa suspending agent, a neutralizing agent, and a reaction propagatingagent. Suitable suspending agents, neutralizing agents, and reactionpropagating agents include, but are not limited to, polymers,N,N-diisopropylethylamine, triethylamine, trimethylamine, sodiumhydroxide, potassium hydroxide, sodium carbonate, and potassiumcarbonate, and combinations thereof. In some embodiments, the suspendingagent is a polymer. In some embodiments, the polymer is a dry polymerthat is useful in improving the suspension and free water control ofcement slurries in fresh and some salt water slurries at elevatedtemperatures. An exemplary polymer that can be used in the cementcompositions of the present application is FSA-3 by Fritz Industries(Mesquite, Tex.). The suspending agent, neutralizing agent, reactionpropagating agent, or a combination thereof can be about 0.1% to about2.5% by weight of the cement, for example, about 0.1% to about 1%, orabout 0.2% to about 0.5% by weight of the cement, or about 0.1%, about0.2%, about 0.3%, about 0.4%, about 0.5%, about 0.75%, about 1%, about1.25%, about 1.5%, about 1.75%, or about 2% by weight of the cement. Insome embodiments, when one or more of a suspending agent, a neutralizingagent, and a reaction propagating agent are present, the amount is about0.4% by weight of the cement.

In some embodiments, the cement composition also contains water. Thecomposition can contain about 1% to about 50% water, by weight of thecomposition, for example, about 10% to about 50%, about 20% to about45%, about 30% to about 40%, or about 1%, about 5%, about 10%, about15%, about 20%, about 25%, about 30%, about 35%, about 39%, about 40%,about 45%, or about 50% water, by weight of the composition. In someembodiments, the amount of water is about 39% by weight of thecomposition. In some embodiments, the amount of water is about 40% byweight of the composition.

Properties of the Cement Composition

In some embodiments, the cement composition of the present applicationexhibits improved elastic properties as compared to the same compositionwithout the polymeric additive. In some embodiments, the cementcomposition has a Young's modulus of about 0.1 GPa to about 40 GPa,about 3 GPa to about 25 GPa, or about 5 GPa to about 20 GPa at apressure of about 0.1 MPa to about 150 MPa, about 10 MPa to about 100MPa, or about 20 MPa to about 40 MPa, at a temperature of about 77° F.to about 450° F., about 125° F. to about 350° F., or about 150° F. toabout 200° F. In some embodiments, the cement composition has a Young'smodulus of about 5 GPa to about 10 GPa at a pressure of about 20 MPa anda temperature of about 180° F.

In some embodiments, addition of the polymeric additive to the cementdoes not decrease the compressive strength of the cement as compared tothe same composition without the polymeric additive. Without wishing tobe bound by any particular theory, it is believed that the triazine ringin the polymeric network, a carbon nitride-type moiety, and thedifunctional monomer, for example, piperazine or any of the otherdifunctional monomers described in this disclosure, are flexible enoughto undergo stretching under stresses. The organic and inorganic blockswithin the polymer network can preserve compressive strength and provideflexibility at the molecular level upon applied stresses. In someembodiments, addition of the polymeric additive to the cement does notdecrease the compressive strength of the cement by more than about 200psi to about 1000 psi as compared to the compressive strength of thesame cement without addition of the polymeric additive. For example, thecompressive strength of the cement does not decrease by more than about200 psi, about 300 psi, about 400 psi, about 500 psi, about 600 psi,about 700 psi, about 800 psi, about 900 psi, or about 1000 psi ascompared to the compressive strength of the same cement without additionof the polymeric additive. In some embodiments, the cement compositionhas a compressive strength of about 1000 psi to about 10,000 psi, about2000 psi to about 8000 psi, or about 3500 psi to about 6500 psi, at apressure of about 0.1 MPa to about 150 MPa, about 10 MPa to about 100MPa, or about 20 MPa to about 40 MPa, at a temperature of about 77° F.to about 450° F., about 125° F. to about 350° F., or about 150° F. toabout 200° F. In some embodiments, the cement composition has acompressive strength of about 5500 psi to about 6500 psi at a pressureof about 20 MPa and a temperature of about 180° F.

In some embodiments, the cement composition of the present applicationexhibits improved toughness or stiffness when exposed to severeconditions (for example, extreme temperatures, pressures, or both). Forexample, the cement composition can exhibit improved elastic properties,such as a reduction in the Young's modulus, without exhibiting asubstantial change in the compressive strength of the composition (forexample, a decrease of the compressive strength of the cement by morethan about 200 psi to about 1000 psi), after exposure to elevatedtemperatures, pressures, or both. In some embodiments, the cementcomposition exhibits a reduction of the Young's modulus of about 5% toabout 30%, such as about 10% to about 25%, about 15% to about 20%, about10% to about 20%, about 10% to about 30%, about 15% to about 30%, about15% to about 25%, or a reduction of about 5%, about 6%, about 7%, about8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%,about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%,about 28%, about 29%, or about 30%, without exhibiting a substantialchange in the compressive strength of the composition (for example, adecrease of the compressive strength of the cement by more than about200 psi to about 1000 psi), after exposure of the cement composition toelevated temperatures, as compared to the Young's modulus andcompressive strength of the cement composition prior to exposure to theelevated temperatures.

Process of Preparing the Cement Composition

Provided in the present application is a method of preparing a cementcomposition, such as a cement composition described in this application.In some embodiments, the method comprises: a) reacting a difunctionalmonomer described in this disclosure with cyanuric chloride to form atriazine polymeric additive; and b) mixing the triazine polymericadditive with cement.

In some embodiments of the method, the molar ratio of the cyanuricchloride reacted with the difunctional monomer is about 1:5 to about5:1. For example, the molar ratio of cyanuric chloride to difunctionalmonomer can be about 1:4: to about 4:1, about 1:3 to about 3:1, about1:2 to about 2:1, about 1:1 to about 1:2, about 1:1 to about 1:1.5, orabout 1:5, about 1:4, about 1:3, about 1:2, about 1:1.5, about 1:1,about 2:1, about 3:1, about 4:1, or about 5:1. In some embodiments, themolar ratio of cyanuric chloride to difunctional monomer is about 1:1 toabout 1:2. In some embodiments, the molar ratio of cyanuric chloride todifunctional monomer is about 1:1.5. In some embodiments, the molarratio of cyanuric chloride to difunctional monomer is about 1:1.

In some embodiments of the method, the molar ratio of cyanuric chlorideto difunctional monomer is about 1:1. In some embodiments, the triazinepolymeric additive that is formed is a polymer with repeat units havingstructure A:

where R¹ represents a difunctional monomer as described in thisapplication and n is about 10 to about 1000, about 50 to about 500, orabout 100 to about 200. In some embodiments of the method, R¹ is

and the triazine polymeric additive that is formed is a polymer withrepeat units having the structure:

where n is about 10 to about 1000, about 50 to about 500, or about 100to about 200.

In some embodiments of the method, the molar ratio of cyanuric chlorideto difunctional monomer is about 1:1.5. In some embodiments, thetriazine polymeric additive that is formed is a polymer with repeatunits having structure B:

where R¹ represents a difunctional monomer as described in thisapplication and n is about 10 to about 1000, about 50 to about 500, orabout 100 to about 200. In some embodiments of the method, R¹ is

and the triazine polymeric additive that is formed is a polymer withrepeat units having the structure:

where n is about 10 to about 1000, about 50 to about 500, or about 100to about 200.

In some embodiments, the method involves reacting the difunctionalmonomer described in this disclosure with cyanuric chloride in thepresence of a solvent, for example, an organic solvent. Suitablesolvents for use in the described methods include any organic solvent,including, but not limited to, 1,4-dioxane, tetrahydrofuran,acetonitrile, dichloromethane, chloroform, N,N-dimethylformamide, andN-methylpyrrolidone. In some embodiments, the solvent is 1,4-dioxane.

In some embodiments, the method involves reacting the difunctionalmonomer described in this disclosure with cyanuric chloride at atemperature of about 15° C. to about 45° C., such as about 20° C. toabout 40° C., or about 25° C. to about 35° C. In some embodiments, themethod involves reacting the difunctional monomer described in thisdisclosure with cyanuric chloride at a temperature of about 25° C. toabout 35° C.

In some embodiments, the method involves reacting the difunctionalmonomer described in this disclosure with cyanuric chloride for a firstperiod of time at a first temperature and then for a second period oftime at a second temperature. In some embodiments, the method involvesreacting the difunctional monomer with cyanuric chloride for a firstperiod of time at a first temperature of about 15° C. to about 45° C.,such as about 20° C. to about 40° C., or about 25° C. to about 35° C.,and then reacting the difunctional monomer with cyanuric chloride for asecond period of time at a second temperature of about 60° C. to about90° C., such as about 65° C. to about 85° C., or about 70° C. to about80° C. In some embodiments, the method involves reacting thedifunctional monomer with cyanuric chloride for a first period of timeat a first temperature of about 25° C. to about 35° C., and then for asecond period of time at a second temperature of about 70° C. to about80° C.

In some embodiments, the method involves reacting the difunctionalmonomer described in this disclosure with cyanuric chloride for a totaltime of about 1 hour to about 36 hours, such as about 6 hours to about30 hours, about 12 hours to about 24 hours, about 18 hours to about 24hours, or about 1, about 2, about 3, about 4, about 5, about 6, about 9,about 12, about 15, about 18, about 21, about 22, about 23, about 24,about 27, about 30, about 33, or about 36 hours. In some embodiments,the method involves reacting the difunctional monomer with cyanuricchloride for a total time of about 18 hours to about 24 hours. In someembodiments the method involves reacting the difunctional monomer withcyanuric chloride for a total time of about 23 hours.

In some embodiments, the method involves reacting the difunctionalmonomer described in this disclosure with cyanuric chloride for a firstperiod of time at a first temperature and then for a second period oftime at a second temperature. In some embodiments, the method involvesreacting the difunctional monomer with cyanuric chloride at a firsttemperature for a first period of time of about 1 hour to about 10hours, such as about 3 hours to about 8 hours, about 4 hours to about 6hours, or about 1 hour, about 2 hours, about 3 hours, about 4 hours,about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9hours, or about 10 hours, and then reacting the difunctional monomerwith cyanuric chloride at a second temperature for a second period oftime of about 12 hours to about 24 hours, such as about 15 hours toabout 21 hours, about 17 hours to about 19 hours, or about 12 hour,about 13 hours, about 14 hours, about 15 hours, about 16 hours, about 17hours, about 18 hours, about 18 hours, about 20 hours, about 21 hours,about 22 hours, about 23 hours, or about 24 hours. In some embodiments,the method involves reacting the difunctional monomer with cyanuricchloride at a first temperature for a first period of time of about 5hours, and then at a second temperature for a second period of time ofabout 18 hours.

In some embodiments, the method involves reacting the difunctionalmonomer with cyanuric chloride for a first period of time of about 5hours at a first temperature of about 25° C. to about 35° C., and thenfor a second period of time of about 18 hours at a second temperature ofabout 70° C. to about 80° C.

Methods Using the Cement Compositions Containing Polymeric Additives

Also provided in this disclosure is a method for providing long-termzonal isolation in oil wells (that is, subterranean formations)including providing to an oil well a cement composition comprisingcement and a triazine polymeric additive described in this disclosure.In some embodiments, the polymeric additive has a structure selectedfrom structure A and structure B.

In some embodiments, the providing occurs above the surface. Theproviding can also occur in the subterranean formation.

The subterranean formation can contain a wellbore containing a steelcasing or multiple casings, a cement sheath in the annuli, andoptionally a packer and a production tubing. The cement sheath, canexperience stresses and annular pressure buildup due to, for example,gas flow through microchannels in the annulus, forming microannuli, andfractures (for example, microfractures), cracks and clefts within oraround the cement sheath, the casing, or the production tubing. This canresult in a deterioration of the mechanical properties of the cement andlead to formation of micro-cracks and fractures, which affect theproduction and increase the cost of operation.

In some embodiments, the polymeric additive improves the tensileproperties of the well cement. In some embodiments, the cementcomposition containing the polymeric additive is stable in downholeconditions. In some embodiments, the polymeric additive interacts withthe cement and forms stable linkages between the additive and thecement. In some embodiments, this interaction at the molecular levelallows for uniform distribution of the stresses experienced in thecement matrix, thus enhancing the properties of the cement.

Also provided in this disclosure is a method of preventing the formationof micro-cracks and fractures in the cement of an oil well (that is,subterranean formation). In some embodiments, the method includesproviding to an oil well a cement composition comprising cement and atriazine polymeric additive described in this disclosure. In someembodiments, the polymeric additive has a structure selected fromstructure A and structure B.

EXAMPLES Example 1 Synthesis and Characterization of Polymer Additives

Two series of polymeric additives (POLY A and POLY B) were synthesizedby reacting cyanuric chloride with the cyclic aliphatic secondary aminepiperazine. The general structures are shown in FIGS. 1A and 1B. Thepolymers in the POLY A series were linear, ladder-type polymers withchloride groups on the polymeric chain (FIG. 1A). The polymers in thePOLY B series were non-linear, branched polymers without any chemicallyreactive groups (FIG. 1B).

Synthesis of POLY A Polymer Containing Piperazine:

The reaction steps for synthesis of a POLY A series polymer containingpiperazine is shown in Scheme 2.

In a reaction vessel, 4.7 grams (g) of piperazine and 20.7 milliliters(mL) of N,N-diisopropylethylamine were mixed in 150 mL 1,4-dioxane at25-35° C. A solution of 10 g of cyanuric chloride in 50 mL 1,4-dioxanewas added to the reaction vessel at 1 milliliter/minute (mL/min) withvigorous stirring. The reaction mixture was stirred at 25-35° C. for 23hours. The precipitates formed were isolated by filtration and washedwith de-ionized water two times and once with acetone. The precipitateswere dried at 25-35° C. under vacuum overnight to result 11.2 g of POLYA in the form of fine powder. The molar ratio of cyanuric chloride topiperazine was 1:1 and polymers with pendant chloride groups wereobtained.

Synthesis of POLY B Polymer Containing Piperazine:

The reaction steps for synthesis of a POLY B series polymer containingpiperazine is shown in Scheme 3.

In a reaction vessel, 7.0 g of piperazine and 33 mL ofN,N-diisopropylethylamine were mixed in 150 mL 1,4-dioxane at 25-35° C.A solution of 10 g of cyanuric chloride in 50 mL 1,4-dioxane was addedto the reaction vessel at 1 mL/min with vigorous stirring. The reactionmixture was stirred at 25-35° C. for 5 hours, followed by heating at70-80° C. for 18 hours. The precipitates formed were isolated byfiltration and washed with de-ionized water two times and once withacetone. The precipitates were dried at 80° C. under vacuum overnight toresult in 11.2 g of POLY B in the form of fine powder. The molar ratioof cyanuric chloride to piperazine was 1:1.5 and polymers without anypendant chloride groups were obtained.

Characterization of POLY A and POLY B Polymers FT-IR Spectroscopy

The formation of the POLY A and POLY B series polymers containingpiperazine was confirmed by FT-IR spectroscopy (see FIG. 2). The FT-IRspectra showed bands in the 1225-1620 centimeters⁻¹ (cm⁻¹) region,corresponding to stretching modes of CN heterocycles, and a band at 805cm⁻¹ , corresponding to the breathing mode of the triazine units. TheFT-IR for the POLY A series polymer demonstrated a shoulder peak at 852cm⁻¹ that confirmed the pendant chloride groups in the polymer networks.The POLY B series polymer lacked the characteristic C—Cl stretchingvibration at 852 cm⁻¹, suggesting that all chloride groups weresubstituted.

Thermogravimetric Analysis

The thermal stability of both the POLY A and POLY B series polymers was380° C., as obtained from the thermogravimetric analyses of the samples(see FIGS. 3A-3B). One distinct characteristic of mass loss in POLY A(FIG. 3A) at around 100° C. can be attributed to the evolution ofchloride at around 100° C. The removal of chloride can be obtained ateven lower temperatures under basic conditions.

Example 2 Cement Slurry Preparation

A series of cement slurries (Formulations A-C) was prepared from thePOLY A and POLY B polymers described in Example 1. The procedure used toprepare each formulation is as follows and the components are shown inTable 1.

Formulation A

Class G cement was blended with a suspending agent (FSA-3, FritzIndustries, Mesquite, Tex.) to provide viscosity and keep cementparticles suspended during the curing process. The blended cementmixture was added into water at 8000 revolutions per minute (rpm),followed by mixing at 12000 rpm for 35 seconds (sec). The cement slurrywas poured into a 1-inch diameter cylinder and was cured at 180° F. and3000 psi for 48 hours (h). The cement samples of 1-inch diameter/2-inchlength were used for mechanical testing.

Formulation B

Class G cement was blended with a suspending agent (FSA-3, FritzIndustries, Mesquite, TX) and the POLY B polymer of Example 1. Theblended cement mixture was added into water at 8000 rpm, followed bymixing at 12000 rpm for 35 sec. The cement slurry was poured into a1-inch diameter cylinder and was cured at 180° F. and 3000 psi for 48 h.The cement samples of 1-inch diameter/2-inch length were used formechanical testing.

Formulation C

Class G cement was blended with a suspending agent (FSA-3, FritzIndustries, Mesquite, Tex.) and the POLY A polymer of Example 1. Theblended cement mixture was added into water at 8000 rpm, followed bymixing at 12000 rpm for 35 sec. The cement slurry was poured into a1-inch diameter cylinder and was cured at 180° F. and 3000 psi for 48 h.The cement samples of 1-inch diameter/2-inch length were used formechanical testing.

TABLE 1 Cement formulations Formulation Components Amount/g % by wt. ofcement Formulation A Class G cement 205.8 Suspending agent 0.82 0.4Water 136.2 Formulation B Class G cement 205.8 Suspending agent 0.82 0.4POLY B 6.2 3 Water 136.2 Formulation C Class G cement 205.8 Suspendingagent 0.82 0.4 POLY A 6.2 3 Water 136.2

Example 3 Mechanical Testing of Cement Formulations Compressive Strength

The compressive strengths of the cement formulations described inExample 2 were tested under confined pressure of 20 MPa at 80° F. and180° F. (See Table 2 and FIG. 4) using a triaxial press capable ofgenerating confining pressures of up to 75 MPa (10,900 psi). The testequipment consisted of an axial loading system, a confining pressuresupply system, and data acquisition software. The cylindrical cementsamples were jacketed and placed between steel end-caps. Staticmechanical properties were measured using strain gauge sensors, whichwere mounted on the sample to measure axial deformation and radialdeformation. A series of laboratory tests was performed to examine thefatigue behavior of cement when subjected to cyclic loading undertriaxial compression conditions. After the sample was placed in atriaxial cell, a confining pressure was applied. The cyclic axial loadwas applied in the form of triangular waveforms. Each sample wasdeformed over three cyclic loading series. In each cyclic loadingseries, a differential stress of 10 MPa was applied during the cyclicloading; various peak axial stresses were applied during cyclic loading.Because uniaxial stress was applied to the sample, this module was usedto calculate Young's modulus and Poisson's ratio to measure samplestrain.

Formulation A, the cement without any polymer additive, showedcompressive strengths of 2520 psi and 5990 psi at 80° F. and 180° F.,respectively. Formulation B, the cement with the POLY B additive, showedcompressive strengths of 3626 psi and 6100 psi at 80° F. and 180° F.,respectively, and Formulation C, the cement with the POLY A additive,showed compressive strengths of 3762 psi and 6163 psi at 80° F. and 180°F., respectively. These results showed that the compressive strengths ofFormulations B and C were not affected by incorporating the polymericadditives. Without wishing to be bound by any theory, it is believedthat the interaction of the additives that contain functional groupssuch as —Cl or nitrogen interact with cement particles, thereby changingthe hydration characteristic of the cement and resulting in FormulationsB and C providing greater compressive strength at the lower temperature(80° F.) tested. At the higher temperature tested (180° F.), thehydration gets saturated for neat cement and cement with additives;therefore, a difference in compressive strength may not be observed.

TABLE 2 Compressive strength of cement formulations at 20 MPaCompressive strength Compressive strength Formulation at 80° F. at 180°F. Formulation A 2520 psi 5990 psi Formulation B 3626 psi 6100 psiFormulation C 3762 psi 6163 psi

Characterization of Formulation C

To confirm the formation of chemical linkages between POLY A and thecement particles, FT-IR spectroscopic analysis of Formulation C wasconducted as shown in FIG. 5. The shoulder peak at 852 cm⁻¹ thatcorresponds to C—Cl in the POLY A additive alone vanished after blendingwith the cement, which confirmed the formation of chemical bondingbetween the polymer and cement particles. This chemical linkage wasformed from the interaction of hydroxyl groups in the cement particleswith the C—Cl group of POLY A. The pH of the cement slurry provided thebasic reaction medium to liberate hydrochloric acid and the curingtemperature provided the right condition for the formation of linkagesbetween the polymer and cement particles. The liberated hydrochloricacid can convert into sodium chloride or calcium chloride upon reactionwith cement constituents.

Elastic Characterization

The elastic characteristic of cement can be determined from Young'smodulus, a mechanical property that measures the stiffness of a solidmaterial and defines the relationship between stress (force per unitarea) and strain (proportional deformation) in a material in the linearelasticity regime of a uniaxial deformation. The Young's modulus ofcement Formulations A-C is shown in Table 3 and FIG. 6. Formulation A,the cement without any polymer additive, showed a Young's modulus of 6.2GPa and 8.9 GPa at 80° F. and 180° F., respectively. Formulation B, thecement with POLY B, demonstrated a Young's modulus of 6.5 GPa and 6.3GPa at 80° F. and 180° F., respectively, and Formulation C, the cementwith POLY A, demonstrated a Young's modulus of 6.6 GPa and 7.4 GPa at80° F. and 180° F., respectively. The reduction in the Young's modulusfor Formulations B and C, as compared to Formulation A, showed that theelastic properties of the cement were improved at the higher temperaturetested (180° F.) as compared to the lower temperature tested (80° F.)upon addition of POLY A and POLY B.

TABLE 3 Young's modulus of cement formulations at 20 MPa Young's modulusYoung's modulus Formulation at 80° F. at 180° F. Formulation A 6.2 GPa8.9 GPa Formulation B 6.5 GPa 6.3 GPa Formulation C 6.6 GPa 7.4 GPa

1. A method for preventing the formation of micro-cracks and fracturesin the cement of an oil well, thereby providing long-term zonalisolation in the well, the method comprising providing to the oil well acement composition comprising cement and a triazine polymeric additivehaving repeat units selected from structure A and structure B:

wherein R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and n is about 10 to about 1000; whereinthe cement composition exhibits improved elastic properties as comparedto the same composition without the polymeric additive.
 2. The method ofclaim 1, wherein R¹ is selected from the group consisting of:

wherein: R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to
 8. 3. The method of claim 2, wherein R¹ is


4. The method of claim 3, wherein the polymeric additive is a polymerhaving repeat units of structure A and has the structure:


5. The method of claim 3, wherein the polymeric additive is a polymerhaving repeat units of structure B and has the structure:


6. The method of claim 1, wherein the amount of polymeric additive inthe cement composition is between about 0.1% to about 10% by weight ofthe cement.
 7. The method of claim 6, wherein the amount of polymericadditive in the cement composition is about 3% by weight of the cement.8. The method of claim 1, wherein the cement composition furthercomprises one or more of a suspending agent, a neutralizing agent, and areaction propagating agent.
 9. The method of claim 8, wherein the one ormore suspending agent, neutralizing agent, and reaction propagatingagent are selected from the group consisting ofN,N-diisopropylethylamine, triethylamine, trimethylamine, sodiumhydroxide, potassium hydroxide, sodium carbonate, and potassiumcarbonate.
 10. The method of claim 1, wherein the cement compositionfurther comprises water.
 11. The method of claim 1, wherein the cementcomposition has a Young's modulus of about 0.1 GPa to about 40 GPa,about 3 GPa to about 25 GPa, or about 5 GPa to about 20 GPa at apressure of about 0.1 MPa to about 150 MPa, about 10 MPa to about 100MPa, or about 20 MPa to about 40 MPa, at a temperature of about 77° F.to about 450° F., about 125° F. to about 350° F., or about 150° F. toabout 200° F.
 12. The method of claim 11, wherein the cement compositionhas a Young's modulus of about 5 GPa to about 10 GPa at a pressure ofabout 20 MPa and a temperature of about 180° F.
 13. The method of claim1, wherein the cement composition has a compressive strength of about1000 psi to about 10,000 psi, about 2000 psi to about 8000 psi, or about3500 psi to about 6500 psi, at a pressure of about 0.1 MPa to about 150MPa, about 10 MPa to about 100 MPa, or about 20 MPa to about 40 MPa, ata temperature of about 77° F. to about 450° F., about 125° F. to about350° F., or about 150° F. to about 200° F.
 14. The method of claim 13,wherein the cement composition has a compressive strength of about 5500psi to about 6500 psi at a pressure of about 20 MPa and a temperature ofabout 180° F.
 15. The method of claim 1, wherein addition of thepolymeric additive to the cement does not decrease the compressivestrength of the cement by more than about 200 psi to about 1000 psi ascompared to the compressive strength of the same cement without additionof the polymeric additive.
 16. A cement composition for providinglong-term zonal isolation in oil wells, comprising: cement; and atriazine polymeric additive selected from a polymer having repeat unitsof structure A and structure B:

wherein R¹ is selected from the group consisting of a cyclic aliphaticsecondary amine, an aromatic diamine, an aromatic diol, an aliphaticdiamine, and an aliphatic diol; and n is about 10 to about
 1000. 17. Thecomposition of claim 16, wherein R¹ is selected from the groupconsisting of.

wherein: R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to
 8. 18. The composition of claim 17, wherein R¹ is


19. The composition of claim 18, wherein the polymeric additive is apolymer having repeat units of structure A and has the structure:


20. The composition of claim 18, wherein the polymeric additive is apolymer having repeat units of structure B and has the structure:


21. The composition of claim 16, wherein the amount of polymericadditive in the cement composition is between about 0.1% to about 10% byweight of the cement.
 22. The composition of claim 21, wherein theamount of polymeric additive in the cement composition is about 3% byweight of the cement.
 23. The composition of claim 16, wherein thecement composition further comprises one or more of a suspending agent,a neutralizing agent, and a reaction propagating agent.
 24. Thecomposition of claim 23, wherein the one or more suspending agent,neutralizing agent, and reaction propagating agent are selected from thegroup consisting of N,N-diisopropylethylamine, triethylamine,trimethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate,and potassium carbonate.
 25. The composition of claim 16, wherein thecement composition further comprises water.
 26. The composition of claim16, wherein the cement composition has a Young's modulus of about 0.1GPa to about 40 GPa, about 3 GPa to about 25 GPa, or about 5 GPa toabout 20 GPa at a pressure of about 0.1 MPa to about 150 MPa, about 10MPa to about 100 MPa, or about 20 MPa to about 40 MPa, at a temperatureof about 77° F. to about 450° F., about 125° F. to about 350° F., orabout 150° F. to about 200° F.
 27. The composition of claim 26, whereinthe cement composition has a Young's modulus of about 5 GPa to about 10GPa at a pressure of about 20 MPa and a temperature of about 180° F. 28.The composition of claim 16, wherein the cement composition has acompressive strength of about 1000 psi to about 10,000 psi, about 2000psi to about 8000 psi, or about 3500 psi to about 6500 psi, at apressure of about 0.1 MPa to about 150 MPa, about 10 MPa to about 100MPa, or about 20 MPa to about 40 MPa, at a temperature of about 77° F.to about 450° F., about 125° F. to about 350° F., or about 150° F. toabout 200° F.
 29. The composition of claim 28, wherein the cementcomposition has a compressive strength of about 5500 psi to about 6500psi at a pressure of about 20 MPa and a temperature of about 180° F. 30.A method of preparing a cement composition, comprising: a) reacting adifunctional monomer with cyanuric chloride to form a triazine polymericadditive; and b) mixing the triazine polymeric additive with cement. 31.The method of claim 30, wherein the difunctional monomer is selectedfrom the group consisting of a cyclic aliphatic secondary amine, anaromatic diamine, an aromatic diol, an aliphatic diamine, and analiphatic diol.
 32. The method of claim 31, wherein the difunctionalmonomer is selected from the group consisting of:

wherein: R² and R³ are each independently selected from the groupconsisting of C₁-C₆ alkyl, C(═O), SO₂, and O; m is 0 to 6; p is 0 to 8;and q is 0 to
 8. 33. The method of claim 32, wherein the difunctionalmonomer is


34. The method of claim 30, wherein the molar ratio of the cyanuricchloride to the difunctional monomer is about 1:1 to about 1:2.
 35. Themethod of claim 34, wherein the molar ratio of the cyanuric chloride tothe difunctional monomer is about 1:1.
 36. The method of claim 35,wherein the triazine polymeric additive has the structure:

wherein n is about 10 to about
 1000. 37. The method of claim 34, whereinthe molar ratio of the cyanuric chloride to the difunctional monomer isabout 1:1.5.
 38. The method of claim 37, wherein the triazine polymericadditive has the structure:

wherein n is about 10 to about
 1000. 39. The method of claim 30, whereinthe amount of polymeric additive in the cement composition is about 0.1%to about 10% by weight of the cement.
 40. The method of claim 39,wherein the amount of polymeric additive in the cement composition isabout 3% by weight of the cement.
 41. The method of claim 30, whereinthe cement composition further comprises one or more of a suspendingagent, a neutralizing agent, and a reaction propagating agent.
 42. Themethod of claim 41, wherein the one or more suspending agent,neutralizing agent, and reaction propagating agent are selected from thegroup consisting of N,N-diisopropylethylamine, triethylamine,trimethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate,and potassium carbonate.
 43. The method of claim 30, wherein the cementcomposition further comprises water.